Hi, @dferrara. No value in Client ID indicates that the API calls can’t be directly attributed to a third party, and are associated with a user instead.
That doesn’t mean that API calls aren’t ultimately being consumed from a third party, only that it’s not directly making calls on their own. Connectors that constantly auth a user’s credentials would be the ones requesting API calls, but Salesforce would attribute those to the user whose creds were being authorized on this report.
Brad Mampe, Salesforce Analyst, Fidelity I'm probably wrong. I may not be right about that.